Copper(I)-carbene complexes and organic electroluminescent devices

ABSTRACT

Devices comprising an organic light emitting device are provided. The devices can include an anode; a cathode; and an organic layer, disposed between the anode and the cathode. The organic layer comprising at least one host material comprising a phosphorescent complex comprising novel phosphorescent trigonal copper carbene complexes. The complex comprise a carbene ligand coordinated to a three coordinate copper atom. The complex may be used in organic light emitting devices. In particular, the complexes may be especially useful in OLEDs used for lighting applications.

This application is a continuation of U.S. application Ser. No. 12/948,396, filed Nov. 17, 2010, now U.S. Pat. No. 8,580,394, which claims priority to U.S. Provisional Application Ser. No. 61/262,804, filed Nov. 19, 2009, U.S. Provisional Application Ser. No. 61/301,362, filed Feb. 4, 2010, U.S. Provisional Application Ser. No. 61/398,808, filed Jul. 1, 2010, and U.S. Provisional Application Ser. No. 61/402,989, filed Sep. 9, 2010, the disclosures of which are herein expressly incorporated by reference in their entirety.

The claimed invention was made by, on behalf of, and/or in connection with one or more of the following parties to a joint university corporation research agreement: Regents of the University of Michigan, Princeton University, The University of Southern California, and the Universal Display Corporation. The agreement was in effect on and before the date the claimed invention was made, and the claimed invention was made as a result of activities undertaken within the scope of the agreement.

FIELD OF THE INVENTION

The present invention relates to phosphorescent copper complexes, and their use in organic light emitting devices (OLEDs). More particularly, the invention relates to phosphorescent complexes comprising a carbene ligand coordinated to a three coordinate copper atom, and devices containing such complexes.

BACKGROUND

Opto-electronic devices that make use of organic materials are becoming increasingly desirable for a number of reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials may have performance advantages over conventional materials. For example, the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage is applied across the device. OLEDs are becoming an increasingly interesting technology for use in applications such as flat panel displays, illumination, and backlighting. Several OLED materials and configurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and 5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full color display. Industry standards for such a display call for pixels adapted to emit particular colors, referred to as “saturated” colors. In particular, these standards call for saturated red, green, and blue pixels. Color may be measured using CIE coordinates, which are well known to the art.

One example of a green emissive molecule is tris(2-phenylpyridine) iridium, denoted Ir(ppy)₃, which has the structure:

In this, and later figures herein, we depict the dative bond from nitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as well as small molecule organic materials that may be used to fabricate organic opto-electronic devices. “Small molecule” refers to any organic material that is not a polymer, and “small molecules” may actually be quite large. Small molecules may include repeat units in some circumstances. For example, using a long chain alkyl group as a substituent does not remove a molecule from the “small molecule” class. Small molecules may also be incorporated into polymers, for example as a pendent group on a polymer backbone or as a part of the backbone. Small molecules may also serve as the core moiety of a dendrimer, which consists of a series of chemical shells built on the core moiety. The core moiety of a dendrimer may be a fluorescent or phosphorescent small molecule emitter. A dendrimer may be a “small molecule,” and it is believed that all dendrimers currently used in the field of OLEDs are small molecules.

As used herein, “top” means furthest away from the substrate, while “bottom” means closest to the substrate. Where a first layer is described as “disposed over” a second layer, the first layer is disposed further away from substrate. There may be other layers between the first and second layer, unless it is specified that the first layer is “in contact with” the second layer. For example, a cathode may be described as “disposed over” an anode, even though there are various organic layers in between.

As used herein, “solution processible” means capable of being dissolved, dispersed, or transported in and/or deposited from a liquid medium, either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed that the ligand directly contributes to the photoactive properties of an emissive material. A ligand may be referred to as “ancillary” when it is believed that the ligand does not contribute to the photoactive properties of an emissive material, although an ancillary ligand may alter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled in the art, a first “Highest Occupied Molecular Orbital” (HOMO) or “Lowest Unoccupied Molecular Orbital” (LUMO) energy level is “greater than” or “higher than” a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level. Since ionization potentials (IP) are measured as a negative energy relative to a vacuum level, a higher HOMO energy level corresponds to an IP having a smaller absolute value (an IP that is less negative). Similarly, a higher LUMO energy level corresponds to an electron affinity (EA) having a smaller absolute value (an EA that is less negative). On a conventional energy level diagram, with the vacuum level at the top, the LUMO energy level of a material is higher than the HOMO energy level of the same material. A “higher” HOMO or LUMO energy level appears closer to the top of such a diagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled in the art, a first work function is “greater than” or “higher than” a second work function if the first work function has a higher absolute value. Because work functions are generally measured as negative numbers relative to vacuum level, this means that a “higher” work function is more negative. On a conventional energy level diagram, with the vacuum level at the top, a “higher” work function is illustrated as further away from the vacuum level in the downward direction. Thus, the definitions of HOMO and LUMO energy levels follow a different convention than work functions.

More details on OLEDs, and the definitions described above, can be found in U.S. Pat. No. 7,279,704, which is incorporated herein by reference in its entirety.

SUMMARY OF THE INVENTION

Novel phosphorescent complexes are provided, the complexes comprising a carbene ligand coordinated to a three coordinate copper atom.

In one aspect, the carbene ligand has the formula:

*C is a divalent carbon atom coordinated to a monovalent copper atom Cu. X₁ and X₂ are substituents independently selected from alkyl, amine, phosphine, heteroalkyl, aryl and heteroaryl. X₁ and X₂ may be further substituted, and X₁ and X₂ are optionally linked to form a cycle. In one aspect, the carbene ligand is monodentate. Preferably, each of X₁ and X₂ independently forms a bond with *C. A first bond is formed between *C and an atom X′₁ in substituent X₁, and a second bond is formed between *C and an atom X′₂ in substituent X₂. X′₁ and X′₂ are independently selected from the group consisting of C, N, O, S and P.

In another aspect, the carbene ligand is monodentate.

In one aspect, X₁ and X₂ are not joined to form a cycle. In another aspect, X₁ and X₂ are joined to form a cycle.

In one aspect, the copper complex is neutral. In another aspect, the copper complex is charged.

In one aspect, the complex has the formula:

Yi is independently selected from the group consisting of alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. Yi is a monodentate ligand or a bidentate ligand. n is 1 or 2. Preferably, n is 2.

In another aspect, the complex has the formula:

Y₁ and Y₂ are substituents that are independently selected from the group consisting of alkyl, heteroalkyl, aryl and heteroaryl. Y₁ and Y₂ may be further substituted. Y₁ and Y₂ are joined. Each of Y₁ and Y₂ form a bond with Cu. A first bond is formed between Cu and an atom Y′₁ in substituent Y₁ and a second bond is formed between Cu and an atom Y′₂ in substituent Y₂. Y′₁ is selected from the group consisting of N, P, *C, O, and S. Y′₂ is selected from the group consisting of N, P, *C, tetravalent carbon, O, and S. Preferably, Y′₁ is N. Preferably, the ring comprising Cu, Y′₁ and Y′₂ is a 5-membered or 6-membered ring.

In another aspect, Y₁ is selected from the group consisting of pyridyl, pyrazole, alkyl amine, imidazole, benzimidazole, triazole, tetrazole, pyridazine, pyrimidine, pyrazine, triazine, tetrazine, oxazole, thiazole, benzoxazole and benzothiazole.

In yet another aspect, Y₁-Y₂ is selected from the group consisting of:

X is selected from the group consisting of NR, O, S, Se, CR₂, and CO. Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. Each ring is further substituted by a substituent selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In another aspect, each R includes a substituent independently selected from the group consisting of carbazole, dibenzofuran, dibenzothiophene, azacarbazole, azadibenzofuran, and azadibenzothiophene.

In yet another aspect, Y₁-Y₂ is selected from the group consisting of:

X is selected from the group consisting of NR, O, S, Se, CR₂, and CO. Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. Each ring is further substituted by a substituent selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, each R includes a substituent independently selected from the group consisting of carbazole, dibenzofuran, dibenzothiophene, azacarbazole, azadibenzofuran, and azadibenzothiophene.

In another aspect, Y_(i) is an unconjugated, monoanionic ligand containing BY₄ ⁻, SO₃Y⁻, CY₄ ⁻, SiO₄ ⁻, OY₂ ⁻, or SY₂ ⁻. Each Y is independently selected from the group consisting of hydrogen, alkyl, aryl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl and heteroaryl.

In one aspect, Y_(i) is BY₄ ⁻. In another aspect, the ligand Yi comprises two monodentate ligands, at least one of which is BY₄ ⁻. Preferably, the ligand Y_(i) has the formula:

More preferably, the ligand Y_(i) that comprises two monodentate ligands, at least one of which is BY₄ ⁻, is selected from the group consisting of:

Y₁ and Y₂ are independently selected from the group consisting of pyridyl, pyrimidyl, pyrazinyl, pyridazinyl, triazinyl, tetrazinyl, triazolyl, tetrazolyl, pyrazolyl, imidazolyl, benzimidazolyl, oxazolyl, thiazolyl, benzoxazolyl, benzothiazolyl and phosphine. Y₁ and Y₂ may be extended by fusion, e.g., benzanulation. Additionally, Y₁ and Y₂ may be further substituted with alkyl, aryl, donor or acceptor groups. Y₃ and Y₄ are independently selected from the group consisting of hydrogen, alkyl, aryl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteralkyl and heteroaryl. In one aspect, Y₃ and Y₄ are joined to form a cycle, may be extended by fusion, e.g., benzanulation.

In another aspect, Y_(i) is a bidentate ligand having the formula BY₄ ⁻. Preferably, the ligand Y_(i) is selected from the group consisting of:

In this aspect, Y₁ is a bidentate chelating ligand having the formula:

Y′₁-Y″₁ represents a neutral, i.e., uncharged, chealting ligand. Y′₁-Y″₁ are capable of coordinating to a metal center.

Specific examples of the Y′₁-Y″₁ ligand include, but are not limited to, ligands having the structure:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

Y₁ and Y₂ are independently selected from the group consisting of pyridyl, pyrimidyl, pyrazinyl, pyridazinyl, triazinyl, tetrazinyl, triazolyl, tetrazolyl, pyrazolyl, imidazolyl, benzimidazolyl, oxazolyl, thiazolyl, benzoxazolyl, benzothiazolyl and phosphine. Y₁ and Y₂ may be extended by fusion, e.g., benzanulation. Additionally, Y₁ and Y₂ may be further substituted with alkyl, aryl, donor or acceptor groups.

Y₃ and Y₄ are independently selected from the group consisting of hydrogen, alkyl, aryl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteralkyl and heteroaryl. In one aspect, Y₃ and Y₄ are joined to form a cycle, which may be extended by fusion, e.g., benzanulation.

In one aspect, Y₁ and Y₂ are the same. Specific examples of ligands where Y₁ and Y₂ are the same include, but are not limited to, ligands selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. C* is a divalent carbon atom. n is 0, 1, or 2. m is 0, 1, or 2.

In one aspect, Y₁ and Y₂ are different. Specific examples of ligands where Y₁ and Y₂ are different include, but are not limited to, ligands selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, Y₃ and Y₄ are selected from the group consisting of:

In one aspect, Y_(i) is SO₃Y⁻. Specific examples of ligands Y_(i) having the formula SO₃Y⁻ include, but are not limited to, ligands having the structure:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, Y_(i) is CY₄ ⁻. Preferably, CY₄ ⁻ has the formula:

Specific examples of ligands Y_(i) having the formula CY₄ ⁻ include, but are not limited to, ligands having the structure:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, Y₃ and Y₄ are selected from the group consisting of:

In another aspect, Y_(i) is SiY₄ ⁻. Specific examples of ligands Y_(i) having the formula SiY₄ ⁻ include, but are not limited to, ligands having the structure:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, Y₃ and Y₄ are selected from the group consisting of:

In another aspect, Y_(i) is OY₂ ⁻. Preferably, OY₂ ⁻ has the formula:

Specific examples of ligands Y_(i) having the formula OY₂ ⁻ include, but are not limited to, ligands having the structure:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, Y₃ and Y₄ are selected from the group consisting of:

In yet another aspect, Y_(i) is SY₂ ⁻. Preferably, SY₂ ⁻ has the formula:

Specific examples of ligands Y_(i) having the formula SY₂ ⁻ include, but are not limited to, ligands having the structure:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, the complex comprises two copper (I) centers. Non-limiting examples of complexes comprising two copper (I) centers include complexes selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In a further aspect, the carbene ligand is selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. z is 1, 2, 3, or 4.

In another aspect, each R includes a substituent independently selected from the group consisting of carbazole, dibenzofuran, dibenzothiophene, azacarbazole, azadibenzofuran, and azadibenzothiophene.

Preferably, the carbene is

More preferably, the carbene is

R′₁ and R′₂ may represent mono, di, tri, or tetra substitutions. R′₁ and R′₂ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. In one aspect, at least one of R′₁ and R′₂ is an alkyl having three or more carbon atoms.

Preferably, the complex is selected from the group consisting of:

Preferably, the complex is selected from the group consisting of:

More preferably, the complex is:

In another aspect, the complex has the formula:

Y₁ and Y₂ are substituents that are independently selected from the group consisting of alkyl, heteroalkyl, aryl and heteroaryl. Y₁ and Y₂ may be further substituted. Y₁ and Y₂ are not joined. Each of Y₁ and Y₂ form a bond with Cu.

In one aspect, the complex is selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In another aspect, the carbene ligand is bidentate. Preferably, the complex is selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. Z is a monodentate ligand.

In one aspect, the complex is included in a polymer. In another aspect, the complex is included in the repeat unit of the polymer. In yet another aspect, the complex is pendant on the polymer. Preferably, the polymer is selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. m is greater than 2. n is 0-20.

In another aspect, the complex is included in a dendritic complex. Preferably, the dendritic complex is

The core is a molecule or a polyvalent element selected from the group consisting of C, Si, Ge, Sn, Pb, N, P, and As. Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. m is greater than 1. n is 0-20.

In yet another aspect, the complex is included in a small molecule.

Devices comprising the phosphorescent complexes are also provided. A first device comprising an organic light emitting device further comprising an anode, a cathode; and an organic layer, disposed between the anode and the cathode. The organic layer further comprising a phosphorescent complex itself comprising a three coordinate copper atom and a carbene ligand. Preferably, the first device is a consumer product. The device may comprise a complex having Formula I, Formula II, Formula III, or Formula IV, as described above. Selections for the substituents, ligands, and complexes described as preferred for the complexes having Formula I, Formula II, Formula III, or Formula IV are also preferred for use in a device that comprises a complex including a complex having Formula I, Formula II, Formula III, or Formula IV. These selections include those described for X₁, X₂, X′₁, X′₂, Y₁, Y₂, Y′₁, Y′₂, Yi, R, X, and Z.

Selections for the substituents, ligands, and complexes described as preferred for the complexes having Formula I, Formula II, Formula III, or Formula IV are also preferred for use in a device that comprises a complex including a complex having Formula I, Formula II, Formula III, or Formula IV. These selections include those described for X₁, X₂, X′₁, X′₂, Y₁, Y₂, Y₃, Y₄, Y₅, Y′₁, Y″₁, Y′₂, Y_(i), R, X, and Z.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does not have a separate electron transport layer.

FIG. 3 shows complexes comprising a carbene ligand coordinated to a three coordinate copper atom.

FIG. 4 shows ¹H-NMR spectrum of Complex 1.

FIG. 5 shows ¹H-NMR spectrum of Complex 2.

FIG. 6 shows ¹H-NMR spectrum of Complex 3.

FIG. 7 shows ¹H-NMR spectrum of Complex 4.

FIG. 8 shows MALDI spectrum of Complex 1.

FIG. 9 shows MALDI spectrum of Complex 2.

FIG. 10 shows MALDI spectrum of Complex 3.

FIG. 11 shows MALDI spectrum of Complex 4.

FIG. 12 shows the absorption spectrum of Complex 1.

FIG. 13 shows the absorption spectrum of Complex 2.

FIG. 14 shows the absorption spectrum of Complex 3.

FIG. 15 shows the absorption spectrum of Complex 4.

FIG. 16A shows absorption spectrum of Complex 4;

FIG. 16B shows the emission spectra of Complex 4.

FIG. 17A shows excitation and emission spectra of Complex 1;

FIG. 17B shows excitation and emission spectra of Complex 2.

FIG. 18A shows excitation and emission spectra of Complex 3;

FIG. 18B shows excitation and emission spectra of Complex 4.

FIG. 19A shows the x-ray structure of Complex 2;

FIG. 19B shows the x-ray structure of Complex 4.

FIG. 20 shows the ³¹P-NMR spectrum of Complex 1.

FIG. 21. shows the ¹H-NMR spectrum of Complex 5.

FIG. 22 shows the X-ray structure of Complex 5.

FIG. 23 shows LCMS spectrum of Complex 6.

FIG. 24A shows corrected emission and excitation spectra of Complex 5 in 2MeTHF at 77K;

FIG. 24B shows corrected emission and excitation spectra of Complex 6 in 2MeTHF at 77K.

FIG. 25 shows a corrected emission spectrum of Complex 4 in PMMA film at room temperature.

FIG. 26A shows a corrected emission spectrum of Complex 4 in CH₂Cl₂ at room temperature;

FIG. 26B shows a corrected emission spectrum of Complex 2 in CH₂Cl₂ at room temperature.

FIG. 27 shows ¹H-NMR spectrum of Complex 7.

FIG. 28A shows ¹H-NMR spectrum of Complex 7;

FIG. 28B shows the ¹¹B-NMR spectrum of Complex 7.

FIG. 29A shows excitation and emission spectra of Complex 7 in 2MeTHF at 77K;

FIG. 29B shows excitation and emission spectra of Complex 8 in 2MeTHF at 77K.

FIG. 30A shows absorption spectrum of Complex 7;

FIG. 30B shows the X-ray structure of Complex 7.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed between and electrically connected to an anode and a cathode. When a current is applied, the anode injects holes and the cathode injects electrons into the organic layer(s). The injected holes and electrons each migrate toward the oppositely charged electrode. When an electron and hole localize on the same molecule, an “exciton,” which is a localized electron-hole pair having an excited energy state, is formed. Light is emitted when the exciton relaxes via a photoemissive mechanism. In some cases, the exciton may be localized on an excimer or an exciplex. Non-radiative mechanisms, such as thermal relaxation, may also occur, but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from their singlet states (“fluorescence”) as disclosed, for example, in U.S. Pat. No. 4,769,292, which is incorporated by reference in its entirety. Fluorescent emission generally occurs in a time frame of less than 10 nanoseconds.

More recently, OLEDs having emissive materials that emit light from triplet states (“phosphorescence”) have been demonstrated. Baldo et al., “Highly Efficient Phosphorescent Emission from Organic Electroluminescent Devices,” Nature, vol. 395, 151-154, 1998; (“Baldo-I”) and Baldo et al., “Very high-efficiency green organic light-emitting devices based on electrophosphorescence,” Appl. Phys. Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporated by reference in their entireties. Phosphorescence is described in more detail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporated by reference.

FIG. 1 shows an organic light emitting device 100. The figures are not necessarily drawn to scale. Device 100 may include a substrate 110, an anode 115, a hole injection layer 120, a hole transport layer 125, an electron blocking layer 130, an emissive layer 135, a hole blocking layer 140, an electron transport layer 145, an electron injection layer 150, a protective layer 155, and a cathode 160. Cathode 160 is a complex cathode having a first conductive layer 162 and a second conductive layer 164. Device 100 may be fabricated by depositing the layers described, in order. The properties and functions of these various layers, as well as example materials, are described in more detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporated by reference.

More examples for each of these layers are available. For example, a flexible and transparent substrate-anode combination is disclosed in U.S. Pat. No. 5,844,363, which is incorporated by reference in its entirety. An example of a p-doped hole transport layer is m-MTDATA doped with F.sub.4-TCNQ at a molar ratio of 50:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. Examples of emissive and host materials are disclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which is incorporated by reference in its entirety. An example of an n-doped electron transport layer is BPhen doped with Li at a molar ratio of 1:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. U.S. Pat. Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their entireties, disclose examples of cathodes including complex cathodes having a thin layer of metal such as Mg:Ag with an overlying transparent, electrically-conductive, sputter-deposited ITO layer. The theory and use of blocking layers is described in more detail in U.S. Pat. No. 6,097,147 and U.S. Patent Application Publication No. 2003/0230980, which are incorporated by reference in their entireties. Examples of injection layers are provided in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety. A description of protective layers may be found in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210, a cathode 215, an emissive layer 220, a hole transport layer 225, and an anode 230. Device 200 may be fabricated by depositing the layers described, in order. Because the most common OLED configuration has a cathode disposed over the anode, and device 200 has cathode 215 disposed under anode 230, device 200 may be referred to as an “inverted” OLED. Materials similar to those described with respect to device 100 may be used in the corresponding layers of device 200. FIG. 2 provides one example of how some layers may be omitted from the structure of device 100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided by way of non-limiting example, and it is understood that embodiments of the invention may be used in connection with a wide variety of other structures. The specific materials and structures described are exemplary in nature, and other materials and structures may be used. Functional OLEDs may be achieved by combining the various layers described in different ways, or layers may be omitted entirely, based on design, performance, and cost factors. Other layers not specifically described may also be included. Materials other than those specifically described may be used. Although many of the examples provided herein describe various layers as comprising a single material, it is understood that combinations of materials, such as a mixture of host and dopant, or more generally a mixture, may be used. Also, the layers may have various sublayers. The names given to the various layers herein are not intended to be strictly limiting. For example, in device 200, hole transport layer 225 transports holes and injects holes into emissive layer 220, and may be described as a hole transport layer or a hole injection layer. In one embodiment, an OLED may be described as having an “organic layer” disposed between a cathode and an anode. This organic layer may comprise a single layer, or may further comprise multiple layers of different organic materials as described, for example, with respect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used, such as OLEDs comprised of polymeric materials (PLEDs) such as disclosed in U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated by reference in its entirety. By way of further example, OLEDs having a single organic layer may be used. OLEDs may be stacked, for example as described in U.S. Pat. No. 5,707,745 to Forrest et al, which is incorporated by reference in its entirety. The OLED structure may deviate from the simple layered structure illustrated in FIGS. 1 and 2. For example, the substrate may include an angled reflective surface to improve out-coupling, such as a mesa structure as described in U.S. Pat. No. 6,091,195 to Forrest et al., and/or a pit structure as described in U.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated by reference in their entireties.

Unless otherwise specified, any of the layers of the various embodiments may be deposited by any suitable method. For the organic layers, preferred methods include thermal evaporation, ink-jet, such as described in U.S. Pat. Nos. 6,013,982 and 6,087,196, which are incorporated by reference in their entireties, organic vapor phase deposition (OVPD), such as described in U.S. Pat. No. 6,337,102 to Forrest et al., which is incorporated by reference in its entirety, and deposition by organic vapor jet printing (OVJP), such as described in U.S. patent application Ser. No. 10/233,470, now U.S. Pat. No. 7,431,968, which is incorporated by reference in its entirety. Other suitable deposition methods include spin coating and other solution based processes. Solution based processes are preferably carried out in nitrogen or an inert atmosphere. For the other layers, preferred methods include thermal evaporation. Preferred patterning methods include deposition through a mask, cold welding such as described in U.S. Pat. Nos. 6,294,398 and 6,468,819, which are incorporated by reference in their entireties, and patterning associated with some of the deposition methods such as ink jet and OVJD. Other methods may also be used. The materials to be deposited may be modified to make them compatible with a particular deposition method. For example, substituents such as alkyl and aryl groups, branched or unbranched, and preferably containing at least 3 carbons, may be used in small molecules to enhance their ability to undergo solution processing. Substituents having 20 carbons or more may be used, and 3-20 carbons is a preferred range. Materials with asymmetric structures may have better solution processibility than those having symmetric structures, because asymmetric materials may have a lower tendency to recrystallize. Dendrimer substituents may be used to enhance the ability of small molecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the invention may be incorporated into a wide variety of consumer products, including flat panel displays, computer monitors, televisions, billboards, lights for interior or exterior illumination and/or signaling, heads up displays, fully transparent displays, flexible displays, laser printers, telephones, cell phones, personal digital assistants (PDAs), laptop computers, digital cameras, camcorders, viewfinders, micro-displays, vehicles, a large area wall, theater or stadium screen, or a sign. Various control mechanisms may be used to control devices fabricated in accordance with the present invention, including passive matrix and active matrix. Many of the devices are intended for use in a temperature range comfortable to humans, such as 18 degrees C. to 30 degrees C., and more preferably at room temperature (20-25 degrees C.).

The materials and structures described herein may have applications in devices other than OLEDs. For example, other optoelectronic devices such as organic solar cells and organic photodetectors may employ the materials and structures. More generally, organic devices, such as organic transistors, may employ the materials and structures.

The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, arylkyl, heterocyclic group, aryl, aromatic group, and heteroaryl are known to the art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32, which are incorporated herein by reference.

Novel trigonal planar copper complexes with a carbene ligand are provided (illustrated in FIG. 3). In particular, the complexes include a monodentate or a bidentate carbene ligand coordinated to a three coordinate copper atom. The complex can be either charged or neutral. These complexes may be advantageously used in organic light emitting devices.

Phosphorescent copper complexes and their incorporation into organic light emitting diodes (OLEDs) is known. See, e.g., Armaroli, N.; Accorsi, G.; Holler, M.; Moudam, O.; Nierengarten, J. F.; Zhou, Z.; Wegh, R. T.; Welter, R., Highly luminescent Cu—I complexes for light-emitting electrochemical cells. Advanced Materials 2006, 18, (10), 1313-1316; Zhang, Q. S.; Zhou, Q. G.; Cheng, Y. X.; Wang, L. X.; Ma, O. G.; Jing, X. B.; Wang, F. S., Highly efficient green phosphorescent organic light-emitting diodes based on Cu—I complexes. Advanced Materials 2004, 16, (5), 432436; Yersin, H.; Monkowius, D.; Czerwieniec, R.; Yu, 1., Copper(I) N-heterocyclic chelate phosphine complexes as blue-emitting materials for organic electroluminescence devices. PCT Int. Appl. (2010), WO 2010031485 A1 20100325; and Ikeda, S.; Nagashima, H.; Ogiwara, T., Copper complexes and their use for luminescent materials, organic electroluminescence elements, and devices containing the elements. Jpn. Kokai Tokkyo Koho (2008), JP 2008303152 A 20081218. However, the reported complexes have limitations. A new class of highly phosphorescent copper complexes, with both carbene and chelating anionic ligands, are provided. It is believed that the carbene ligand will give the complex stability and enhance phosphorescence. The chelating anionic ligand is a high triplet energy ligand, capable of supporting metal-to-ligand charge transfer interactions. The complexes in this class may provide high energy phosphorescence, which can be useful in the fabrication of doped OLEDs, in which the copper complex is an emissive dopant. These materials may also be used as host materials to support an emissive dopant in an OLED structure. For example, a dipyridyl borate complex in this class of compounds has an emission maximum of 475 nm and a photoluminescence efficiency of 0.95 in the solid state. Suitable substitution of the pyridyl groups can red or blue shift this emission substantially. The ability to tune emission energies may make these copper complexes excellent emitters and host materials for OLEDs. It is thought that the emission energy may be shifted high enough to make these compounds suitable host materials for deep blue to violet emissive dopants.

Phosphorescent OLEDs have relied largely on heavy metal complexes as emitters. In particular, devices often utilize emitters containing Ir or Pt to induce spin orbit coupling. Tetrahedral copper complexes have been reported, and are known to phosphoresce at room temperature. However, tetrahedral copper complexes may have certain limitations. In particular, flattening distortions may increase the non-radiative rate, which leads to a decrease in luminescence efficiency. Trigonal planar copper carbene complexes have now been found to give efficient phosphorescence at room temperature. We believe that this is the first observation of phosphorescence from trigonal planar copper complexes.

Trigonal planar copper complexes may also have several advantages for use in OLEDs. In particular, the trigonal planar copper complexes have comparatively short lifetimes, in the tens of microsecond range (see Table 1). Table 1 shows the lifetimes of several different trigonal planar copper carbene complexes. Generally, the lifetime of the trigonal copper complex is longer than an Ir complex (i.e., 1-10 μs) but shorter than that of a platinum porphyrin complex.

TABLE 1 λmax 77K Solid state QY Lifetime 77K 2MeTHF 2MeTHF Complex 1 31.8% τ₁ = 1143 μs (30.1%) 440 nm τ₂ = 458.5 μs (69.6%) Complex 2  2.6% τ = 10.6 μs 605 nm Complex 3  0.5% τ = 0.7 μs 615 nm Complex 4 43.3% τ = 55.9 μs 545 nm   33% (PMMA film)

In particular, several of the copper complexes provide efficient phosphorescence at room temperature and have comparatively short lifetimes, i.e., in the 10's of microsecond range. Table 2 shows the lifetimes of several different trigonal planar copper carbene complexes.

TABLE 2 Solid Lifetime 77K state QY 2MeTHF λmax 77K 2MeTHF Complex 1 31.8% τ = 656 μs 443 nm Complex 2  2.6% τ₁ = 1.8 μs (24%) 630 nm τ₂ = 4.6 μs (76%) Complex 3  0.5% τ = 0.7 μs 645 nm Complex 4   58% τ = 55.9 μs 555 nm   35% (PMMA film) Complex 5 13.5% τ = 2312 μs 562; 574; 610; 660 nm Complex 6   21% τ = 55 μs 560 nm

Trigonal planar copper complexes may also be particularly useful in OLEDs used for certain applications. In particular, copper complexes provide a broader line spectrum which is especially useful for lighting applications. Further, a device comprising a trigonal planar copper complex in combination with only one other complex may cover red, green, and blue colors. For example, a device comprising a trigonal planar copper complex and a blue emitter may cover all colors required for lighting.

Novel phosphorescent complexes are provided, the complexes comprising a carbene ligand coordinated to a three coordinate copper atom.

In one aspect, the carbene ligand has the formula:

*C is a divalent carbon atom coordinated to a monovalent copper atom Cu. X₁ and X₂ are substituents independently selected from alkyl, amine, phosphine, heteroalkyl, aryl and heteroaryl. X₁ and X₂ may be further substituted, and X₁ and X₂ are optionally linked to form a cycle. In one aspect, the carbene ligand is monodentate. Preferably, each of X₁ and X₂ independently forms a bond with *C. A first bond is formed between *C and an atom X′₁ in substituent X₁, and a second bond is formed between *C and an atom X′₂ in substituent X₂. X′₁ and X′₂ are independently selected from the group consisting of C, N, O, S and P.

In another aspect, the carbene ligand is monodentate.

In one aspect, X₁ and X₂ are not joined to form a cycle. In another aspect, X₁ and X₂ are joined to form a cycle.

In one aspect, the copper complex is neutral. Neutral complexes may be particularly beneficial for use in OLEDs. For example, a neutral complex can be deposited via vapor deposition. In another aspect, the copper complex is charged.

In one aspect, the complex has the formula:

Yi is independently selected from the group consisting of alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. Yi is a monodentate ligand or a bidentate ligand. n is 1 or 2. Preferably, n is 2.

In another aspect, the complex has the formula:

Y₁ and Y₂ are substituents that are independently selected from the group consisting of alkyl, heteroalkyl, aryl and heteroaryl. Y₁ and Y₂ may be further substituted. Y₁ and Y₂ are joined. Each of Y₁ and Y₂ form a bond with Cu. A first bond is formed between Cu and an atom Y′₁ in substituent Y₁ and a second bond is formed between Cu and an atom Y′₂ in substituent Y₂. Y′₁ is selected from the group consisting of N, P, *C, O, and S. Y′₂ is selected from the group consisting of N, P, *C, tetravalent carbon, O, and S. Preferably, Y′₁ is N.

The Cu atom, the Y′₁ atom and the Y′₂ atom in the complex are included in a ring that can be, for example, a 4-membered, 5-membered, 6-membered, 7-membered, or 8-membered ring. Preferably, the ring comprising Cu, Y′₁ and Y′₂ is a 5-membered or 6-membered ring.

In one aspect, Y₁ is selected from the group consisting of pyridyl, pyrazole, alkyl amine, imidazole, benzimidazole, triazole, tetrazole, pyridazine, pyrimidine, pyrazine, triazine, tetrazine, oxazole, thiazole, benzoxazole and benzothiazole.

In another aspect, Y₁-Y₂ is selected from the group consisting of:

X is selected from the group consisting of NR, O, S, Se, CR₂, and CO. Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. Each ring is further substituted by a substituent selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, each R includes a substituent independently selected from the group consisting of carbazole, dibenzofuran, dibenzothiophene, azacarbazole, azadibenzofuran, and azadibenzothiophene.

In yet another aspect, Y₁-Y₂ is selected from the group consisting of:

X is selected from the group consisting of NR, O, S, Se, CR₂, and CO. Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. Each ring is further substituted by a substituent selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, each R includes a substituent independently selected from the group consisting of carbazole, dibenzofuran, dibenzothiophene, azacarbazole, azadibenzofuran, and azadibenzothiophene.

In another aspect, Y_(i) is an unconjugated, monoanionic ligand containing BY₄ ⁻, SO₃Y⁻, CY₄ ⁻, SiO₄ ⁻, OY₂ ⁻, or SY₂ ⁻. Each Y is independently selected from the group consisting of hydrogen, alkyl, aryl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteralkyl and heteroaryl.

In one aspect, Y_(i) is BY₄ ⁻. In another aspect, the ligand Yi comprises two monodentate ligands, at least one of which is BY₄ ⁻. Preferably, the ligand Y_(i) has the formula:

More preferably, the ligand Y_(i) that comprises two monodentate ligands, at least one of which is BY₄ ⁻, is selected from the group consisting of:

Y₁ and Y₂ are independently selected from the group consisting of pyridyl, pyrimidyl, pyrazinyl, pyridazinyl, triazinyl, tetrazinyl, triazolyl, tetrazolyl, pyrazolyl, imidazolyl, benzimidazolyl, oxazolyl, thiszolyl, benzoxazolyl, benzothiazolyl and phosphine. Y₁ and Y₂ may be extended by fusion, e.g., benzanulation. Additionally, Y₁ and Y₂ may be further substituted with alkyl, aryl, donor or acceptor groups. Y₃ and Y₄ are independently selected from the group consisting of hydrogen, alkyl, aryl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteralkyl and heteroaryl. In one aspect, Y₃ and Y₄ are joined to form a cycle, may be extended by fusion, e.g., benzanulation.

In another aspect, Y_(i) is a bidentate ligand having the formula BY₄ ⁻. Preferably, the ligand Y_(i) is selected from the group consisting of:

In this aspect, Y₁ is a bidentate chelating ligand having the formula:

Y′₁-Y″₁ represents a neutral, i.e., uncharged, chelating ligand. Y′₁-Y″₁ are capable of coordinating to a metal center.

Specific examples of the Y′₁-Y″₁ ligand include, but are not limited to, ligands having the structure:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

Y₁ and Y₂ are independently selected from the group consisting of pyridyl, pyrimidyl, pyrazinyl, pyridazinyl, triazinyl, tetrazinyl, triazolyl, tetrazolyl, pyrazolyl, imidazolyl, benzimidazolyl, oxazolyl, thiszolyl, benzoxazolyl, benzothiazolyl and phosphine. Y₁ and Y₂ may be extended by fusion, e.g., benzanulation. Additionally, Y₁ and Y₂ may be further substituted with alkyl, aryl, donor or acceptor groups.

Y₃ and Y₄ are independently selected from the group consisting of hydrogen, alkyl, aryl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteralkyl and heteroaryl. In one aspect, Y₃ and Y₄ are joined to form a cycle, which may be extended by fusion, e.g., benzanulation.

In one aspect, Y₁ and Y₂ are the same. Specific examples of ligands where Y₁ and Y₂ are the same include, but are not limited to, ligands selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. C* is a divalent carbon atom. n is 0, 1, or 2. m is 0, 1, or 2.

In one aspect, Y₁ and Y₂ are different. Specific examples of ligands where Y₁ and Y₂ are different include, but are not limited to, ligands selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, Y₃ and Y₄ are selected from the group consisting of:

In one aspect, Y_(i) is SO₃Y⁻. Specific examples of ligands Y_(i) having the formula SO₃Y⁻ include, but are not limited to, ligands having the structure:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, Y_(i) is CY₄ ⁻. Preferably, CY₄ ⁻ has the formula:

Specific examples of ligands Y_(i) having the formula CY₄ ⁻ include, but are not limited to, ligands having the structure:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, Y₃ and Y₄ are selected from the group consisting of:

In another aspect, Y_(i) is SiY₄ ⁻. Specific examples of ligands Y_(i) having the formula SiY₄ ⁻ include, but are not limited to, ligands having the structure:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, Y₃ and Y₄ are selected from the group consisting of:

In another aspect, Y_(i) is OY₂ ⁻. Preferably, OY₂ ⁻ has the formula:

Specific examples of ligands Y_(i) having the formula OY₂ ⁻ include, but are not limited to, ligands having the structure:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, Y₃ and Y₄ are selected from the group consisting of:

In yet another aspect, Y_(i) is SY₂ ⁻. Preferably, SY₂ ⁻ has the formula:

Specific examples of ligands Y_(i) having the formula SY₂ ⁻ include, but are not limited to, ligands having the structure:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, the complex comprises two copper (I) centers. Non-limiting examples of complexes comprising two copper (I) centers include complexes selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In a further aspect, the carbene ligand is selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. z is 1, 2, 3, or 4.

Preferably, the carbene is

More preferably, the carbene is

R′₁ and R′₂ may represent mono, di, tri, or tetra substitutions. R′₁ and R′₂ are independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. In one aspect, at least one of R′₁ and R′₂ is an alkyl having three or more carbon atoms.

Preferably, the complex is selected from the group consisting of:

Preferably, the complex is selected from the group consisting of:

More preferably, the complex is:

In another aspect, the complex has the formula:

Y₁ and Y₂ are substituents that are independently selected from the group consisting of alkyl, heteroalkyl, aryl and heteroaryl. Y₁ and Y₂ may be further substituted. Y₁ and Y₂ are not joined. Each of Y₁ and Y₂ form a bond with Cu.

In one aspect, the complex is selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In another aspect, the carbene ligand is bidentate. Preferably, the complex is selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. Z is a monodentate ligand.

In one aspect, the complex is included in a polymer. In another aspect, the complex is included in the repeat unit of the polymer. In yet another aspect, the complex is pendant on the polymer. Preferably, the polymer is selected from the group consisting of:

Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. m is greater than 2. n is 0-20.

In another aspect, the complex is included in a dendritic complex. Preferably, the dendritic complex is

The core is a molecule or a polyvalent element selected from the group consisting of C, Si, Ge, Sn, Pb, N, P, and As. Each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl. m is greater than 1. n is 0-20.

In yet another aspect, the complex is included in a small molecule.

Devices comprising the phosphorescent complexes are also provided. A first device comprising an organic light emitting device further comprising an anode, a cathode; and an organic layer, disposed between the anode and the cathode. The organic layer further comprising a phosphorescent complex itself comprising a three coordinate copper atom and a carbene ligand. Preferably, the first device is a consumer product. The device may comprise a complex having Formula I, Formula II, Formula III, or Formula IV, as described above. Selections for the substituents, ligands, and complexes described as preferred for the complexes having Formula I, Formula II, Formula III, or Formula IV are also preferred for use in a device that comprises a complex including a complex having Formula I, Formula II, Formula III, or Formula IV. These selections include those described for X₁, X₂, X′₁, X′₂, Y₁, Y₂, Y′₁, Y′₂, Yi, R, X, and Z.

Selections for the substituents, ligands, and complexes described as preferred for the complexes having Formula I, Formula II, Formula III, or Formula IV are also preferred for use in a device that comprises a complex including a complex having Formula I, Formula II, Formula III, or Formula IV. These selections include those described for X₁, X₂, X′₁, X′₂, Y₁, Y₂, Y₃, Y₄, Y₅, Y″₁, Y′₂, Y_(i), R, X, and Z.

Such devices may contain the trigonal copper complex as a neat thin film. In particular, an OLED comprising a pure film of the complex may have a higher luminescent efficiency than an OLED that comprises the complex doped with another material. Previously, it was thought that complexes cannot be used in pure films because of self-quenching. However, the trigonal copper complexes provided herein may not demonstrate the self-quenching problems seen in other complexes.

The materials described herein as useful for a particular layer in an organic light emitting device may be used in combination with a wide variety of other materials present in the device. For example, emissive dopants disclosed herein may be used in conjunction with a wide variety of hosts, transport layers, blocking layers, injection layers, electrodes and other layers that may be present. The materials described or referred to below are non-limiting examples of materials that may be useful in combination with the complexes disclosed herein, and one of skill in the art can readily consult the literature to identify other materials that may be useful in combination.

In addition to and/or in combination with the materials disclosed herein, many hole injection materials, hole transporting materials, host materials, dopant materials, exiton/hole blocking layer materials, electron transporting and electron injecting materials may be used in an OLED. Non-limiting examples of the materials that may be used in an OLED in combination with materials disclosed herein are listed in Table 3 below. Table 3 lists non-limiting classes of materials, non-limiting examples of complexes for each class, and references that disclose the materials.

TABLE 3 MATERIAL EXAMPLES OF MATERIAL PUBLICATIONS Hole injection materials Phthalocyanine and porphryin complexes

Appl. Phys. Lett. 69, 2160 (1996) Starburst triarylamines

J. Lumin. 72-74, 985 (1997) CF_(x) Fluorohydrocarbon polymer

Appl. Phys. Lett. 78, 673 (2001) Conducting polymers (e.g., PEDOT:PSS, polyaniline, polypthiophene)

Synth. Met. 87, 171 (1997) WO2007002683 Phosphonic acid and sliane SAMs

US20030162053 Triarylamine or polythiophene polymers with conductivity dopants

EA01725079A1

Arylamines complexed with metal oxides such as molybdenum and tungsten oxides

SID Symposium Digest, 37, 923 (2006) WO2009018009 p-type semiconducting organic complexes

US20020158242 Metal organometallic complexes

US20060240279 Cross-linkable complexes

US20080220265 Hole transporting materials Triarylamines (e.g., TPD, α-NPD)

Appl. Phys. Lett. 51, 913 (1987)

U.S. Pat. No. 5,061,569

EP650955

J. Mater. Chem. 3, 319 (1993)

Appl. Phys. Lett. 90, 183503 (2007)

Appl. Phys. Lett. 90, 183503 (2007) Triaylamine on spirofluorene core

Synth. Met. 91, 209 (1997) Arylamine carbazole complexes

Adv. Mater. 6, 677 (1994), US20080124572 Triarylamine with (di)benzothiophene/ (di)benzofuran

US20070278938, US20080106190 Indolocarbazoles

Synth. Met. 111, 421 (2000) Isoindole complexes

Chem. Mater. 15, 3148 (2003) Metal carbene complexes

US20080018221 Phosphorescent OLED host materials Red hosts Arylcarbazoles

Appl. Phys. Lett. 78, 1622 (2001) Metal 8-hydroxy- quinolates (e.g., Alq₃, BAlq)

Nature 395, 151 (1998)

US20060202194

WO2005014551

WO2006072002 Metal phenoxybenzothiazole complexes

Appl. Phys. Lett. 90, 123509 (2007) Conjugated oligomers and polymers (e.g., polyfluorene)

Org. Electron. 1, 15 (2000) Aromatic fused rings

WO2009066779, WO2009066778, WO2009063833, US20090045731, US20090045730, WO2009008311, US20090008605, US20090009065 Zinc complexes

WO2009062578 Green hosts Arylcarbazoles

Appl. Phys. Lett. 78, 1622 (2001)

US20030175553

WO2001039234 Aryltriphenylene complexes

US20060280965

US20060280965

WO2009021126 Donor acceptor type molecules

WO2008056746 Aza-carbazole/DBT/ DBF

JP2008074939 Polymers (e.g., PVK)

Appl. Phys. Lett. 77, 2280 (2000) Spirofluorene complexes

WO2004093207 Metal phenoxybenzooxazole complexes

WO2005089025

WO2006132173

JP200511610 Spirofluorene-carbazole complexes

JP2007254297

JP2007254297 Indolocabazoles

WO2007063796

WO2007063754 5-member ring electron deficient heterocycles (e.g., triazole, oxadiazole)

J. Appl. Phys. 90, 5048 (2001)

WO2004107822 Tetraphenylene complexes

US20050112407 Metal phenoxypyridine complexes

WO2005030900 Metal coordination complexes (e.g., Zn, Al with N{circumflex over ( )}N ligands)

US20040137268, US20040137267 Blue hosts Arylcarbazoles

Appl. Phys. Lett. 82, 2422 (2003)

US20070190359 Dibenzothiophene/ Dibenzofuran-carbazole complexes

WO2006114966, US20090167162

US20090167162

WO2009086028

US20090030202, US20090017330 Silicon aryl complexes

US20050238919

WO2009003898 Silicon/Germanium aryl complexes

EP2034538A Aryl benzoyl ester

WO2006100298 High triplet metal organometallic complex

U.S. Pat. No. 7,154,114 Phosphorescent dopants Red dopants Heavy metal porphyrins (e.g., PtOEP)

Nature 395, 151 (1998) Iridium(III) organometallic complexes

Appl. Phys. Lett. 78, 1622 (2001)

US2006835469

US2006835469

US20060202194

US20060202194

US20070087321

US20070087321

Adv. Mater. 19, 739 (2007)

WO2009100991

WO2008101842 Platinum(II) organometallic complexes

WO2003040257 Osminum(III) complexes

Chem. Mater. 17, 3532 (2005) Ruthenium(II) complexes

Adv. Mater. 17, 1059 (2005) Rhenium (I), (II), and (III) complexes

US20050244673 Green dopants Iridium(III) organometallic complexes

Inorg. Chem. 40, 1704 (2001)

US20020034656

U.S. Pat. No. 7,332,232

US20090108737

US20090039776

U.S. Pat. No. 6,921,915

U.S. Pat. No. 6,687,266

Chem. Mater. 16, 2480 (2004)

US20070190359

US 20060008670 JP2007123392

Adv. Mater. 16, 2003 (2004)

Angew. Chem. Int. Ed. 2006, 45, 7800

WO2009050290

US20090165846

US20080015355 Monomer for polymeric metal organometallic complexes

U.S. Pat. No. 7,250,226, U.S. Pat. No. 7,396,598 Pt(II) organometallic complexes, including polydentated ligands

Appl. Phys. Lett. 86, 153505 (2005)

Appl. Phys. Lett. 86, 153505 (2005)

Chem. Lett. 34, 592 (2005)

WO2002015645

US20060263635 Cu complexes

WO2009000673 Gold complexes

Chem. Commun. 2906 (2005) Rhenium(II) complexes

Inorg. Chem. 42, 1248 (2003) Deuterated organometallic complexes

US20030138657 Organometallic complexes with two or more metal centers

US20030152802

U.S. Pat. No. 7,090,928 Blue dopants Iridium(III) organometallic complexes

WO2002002714

WO2006009024

US20060251923

U.S. Pat. No. 7,393,599, WO2006056418, US20050260441, WO2005019373

U.S. Pat. No. 7,534,505

U.S. Pat. No. 7,445,855

US20070190359, US20080297033

U.S. Pat. No. 7,338,722

US20020134984

Angew. Chem. Int. Ed. 47, 1 (2008)

Chem. Mater. 18, 5119 (2006)

Inorg. Chem. 46, 4308 (2007)

WO2005123873

WO2005123873

WO2007004380

WO2006082742 Osmium(II) complexes

U.S. Pat. No. 7,279,704

Organometallics 23, 3745 (2004) Gold complexes

Appl. Phys. Lett. 74, 1361 (1999) Platinum(II) complexes

WO2006098120, WO2006103874 Exciton/hole blocking layer materials Bathocuprine complexes (e.g., BCP, BPhen)

Appl. Phys. Lett. 75, 4 (1999)

Appl. Phys. Lett. 79, 449 (2001) Metal 8-hydroxy- quinolates (e.g., BAlq)

Appl. Phys. Lett. 81, 162 (2002) 5-member ring electron deficient heterocycles such as triazole, oxadiazole, imidazole, benzoimidazole

Appl. Phys. Lett. 81, 162 (2002) Triphenylene complexes

US20050025993 Fluorinated aromatic complexes

Appl. Phys. Lett. 79, 156 (2001) Phenothiazine-S-oxide

WO2008132085 Electron transporting materials Anthracene- benzoimidazole complexes

WO2003060956

US20090179554 Aza triphenylene derivatives

US20090115316 Anthracene- benzothiazole complexes

Appl. Phys. Lett. 89, 063504 (2006) Metal 8-hydroxy- quinolates (e.g., Alq₃, Zrq₄)

Appl. Phys. Lett. 51, 913 (1987) U.S. Pat. No. 7,230,107 Metal hydroxy- benoquinolates

Chem. Lett. 5, 905 (1993) Bathocuprine complexes such as BCP, BPhen, etc

Appl. Phys. Lett. 91, 263503 (2007)

Appl. Phys. Lett. 79, 449 (2001) 5-member ring electron deficient heterocycles (e.g., triazole, oxadiazole, imidazole, benzoimidazole)

Appl. Phys. Lett. 74, 865 (1999)

Appl. Phys. Lett. 55, 1489 (1989)

Jpn. J. Apply. Phys. 32, L917 (1993) Silole complexes

Org. Electron. 4, 113 (2003) Arylborane complexes

J. Am. Chem. Soc. 120, 9714 (1998) Fluorinated aromatic complexes

J. Am. Chem. Soc. 122, 1832 (2000) Fullerene (e.g., C60)

US20090101870 Triazine complexes

US20040036077 Zn (N{circumflex over ( )}N) complexes

U.S. Pat. No. 6,528,187

EXPERIMENTAL Complex Examples

Several of the complexes were synthesized as follows:

Example 1. Synthesis of Complex 1

Chloro[1,3-bis(2,6-di-1-propylphenyl)imidazol-2-ylidene]copper(I) (487.59 mg, 0.25 mmol) and silver triflate (64.2 mg, 0.25 mmol) were mixed under nitrogen in 25 mL flask and 10 mL of dry THF were added. Reaction mixture was stirred at RT for 30 minutes. Solution of 1,2-bis(diphenylphosphino)benzene (111.6 mg, 0.25 mmol) in dry THF (5 mL) was added. Reaction mixture was stirred at RT overnight. Resulting mixture was filtered through Celite® and solvent was evaporated on rotovap. Recrystallization from CH₂Cl₂ by vapor diffusion of Et₂O gave 130 mg (49.6%) of white needle crystals. Structure confirmed by ¹H-NMR spectrum of [(IPR)Cu(dppbz)]OTf (CDCl₃, 400 MHz).

Example 2. Synthesis of Complex 2

Chloro[1,3-bis(2,6-di-1-propylphenyl)imidazol-2-ylidene]copper(I) (121.9 mg, 0.25 mmol) and silver triflate (64.2 mg, 0.25 mmol) were mixed under nitrogen in 25 mL flask and 10 mL of dry THF were added. Reaction mixture was stirred at RT for 30 minutes. Solution of 1,10-phenanthroline (45.05 mg, 0.25 mmol) in dry THF (5 mL) was added. Reaction mixture turned yellow and was stirred at RT overnight. Resulting mixture was filtered through Celite® and solvent was evaporated on rotovap. Recrystallization from CH₂Cl₂ by vapor diffusion of Et₂O gave 120 mg (61.4%) of yellow crystals. Anal. calcd. for C₄₀H₄₄CuF₃N₄O₃S: C, 61.48; H, 5.68; N, 7.17. Found: C, 61.06; H, 5.61; N, 7.14. Structure was confirmed by ¹H-NMR spectrum of [(IPR)Cu(phen)]OTf (CDCl₃, 400 MHz).

Example 3. Synthesis of Complex 3

Chloro[1,3-bis(2,6-di-1-propylphenyl)imidazol-2-ylidene]copper(I) (195.1 mg, 0.4 mmol) and silver triflate (102.7 mg, 0.4 mmol) were mixed under nitrogen in 25 mL flask and 10 mL of dry THF were added. Reaction mixture was stirred at RT for 30 minutes. Solution of 2,2′-bipyridine (62.4 mg, 0.4 mmol) in dry THF (5 mL) was added. Reaction mixture turned orange and was stirred at RT overnight. Resulting mixture was filtered through Celite® and solvent was evaporated on rotovap. Recrystallization from CH₂Cl₂ by vapor diffusion of Et₂O gave 215 mg (70.9%) of orange crystals. Anal. calcd. for C₃₈H₄₄CuF₃N₄O₃S: C, 60.26; H, 5.86; N, 7.40; Found: C, 60.18; H, 5.82; N, 7.38. Structure was confirmed by ¹H-NMR spectrum of [(IPR)Cu(bipy)]OTf (CDCl₃, 400 MHz).

Example 4. Synthesis of Complex 4

2-(2-Pyridyl)benzimidazole (78.1 mg, 0.4 mmol) was dissolved in 10 mL of dry THF under N₂ and this solution was transferred via cannula to suspension of sodium hydride (17.6 mg, 0.44 mmol, 60% in mineral oil) in dry THF. Reaction mixture was stirred at RT for 1 h and then chloro[1,3-bis(2,6-di-1-propylphenyl)imidazol-2-ylidene]copper(I) (195.1 mg, 0.4 mmol) was added. Reaction mixture was stirred at RT for 3 h. The resulting mixture was filtered through Celite® and solvent was removed by rotary evaporation. Recrystallization by vapor diffusion of Et₂O into a CH₂Cl₂ solution of product gave 154 mg (59.5%) of dark yellow crystals. Anal. calcd. for C₃₉H₄₄CuN₅: C, 72.47; H, 6.86; N, 10.48. Found: C, 72.55; H, 6.94; N, 10.84.

Example 5. Synthesis of Complex 5

1-(1H-benzimidazol-2-yl)-isoquinoline (46 mg, 0.19 mmol) was dissolved in 10 mL of dry THF under N₂ and this solution was transferred via cannula to suspension of sodium hydride (8.36 mg, 0.209 mmol, 60% in mineral oil) in dry THF. The reaction mixture was stirred at RT for 1 h and then chloro[1,3-bis(2,6-di-1-propylphenyl)imidazol-2-ylidene]copper(I) (92.6 mg, 0.19 mmol) was added. The reaction mixture was stirred at RT for 3 h. The resulting mixture was filtered through Celite® and solvent was removed by rotary evaporation. Recrystallization by vapor diffusion of Et₂O into a CH₂Cl₂ solution of product gave 50 mg (38%) of orange crystals.

Example 6. Synthesis of Complex 6

2-(2-Pyridyl)benzimidazole (78.1 mg, 0.4 mmol) was dissolved in 10 mL of dry THF under N₂ and this solution was transferred via cannula to suspension of sodium hydride (17.6 mg, 0.44 mmol, 60% in mineral oil) in dry THF. The reaction mixture was stirred at RT for 1 h and then chloro[1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene]copper(I) (161.4 mg, 0.4 mmol) was added. The reaction mixture was stirred at RT for 3 h. The resulting mixture was filtered through Celite®. Solvent was removed by rotary evaporation and 178 mg (79%) of light-yellow solid was obtained.

Example 7. Synthesis of Complex 7

Sodium dimethylbis(2-pyridyl)borate Na[(CH₃)₂B(py)₂] (66 mg, 0.3 mmol) and chloro[1,3-bis(2,6-di-1-propylphenyl)-4,5-dihydroimidazol-2-ylidene]copper(I) (SIPr)CuCl (146.9 mg, 0.3 mmol) were mixed under N₂ atmosphere in 25 mL flask. Freshly distilled THF (10 ml) was added and reaction mixture was stirred at RT for 1 h. Resulting mixture was filtered through Celite® and solvent was evaporated on rotovap. Recrystallization from acetone/hexane gave 85 mg (43.5%) of white solid. ¹H-NMR (acetone-d₆, 400 MHz, ppm): δ −0.28 (s, 6H), 1.14 (d, 12H), 1.32 (d, 12H), 3.56 (sept, 4H), 4.21 (s, 4H), 6.56-6.60 (m, 2H), 7.20 (td, 2H), 7.27-7.30 (m, 6H), 7.38 (t, 2H), 7.50 (d, 2H).

Example 8. Synthesis of Complex 8

Sodium dimethylbis(2-pyridyl)borate Na[(CH₃)₂B(py)₂] (68.7 mg, 0.312 mmol) and chloro[1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene]copper(I) (106 mg, 0.26 mmol) were mixed under N₂ atmosphere in 25 mL flask. Freshly distilled THF (10 ml) was added and reaction mixture was stirred at RT for 1 h. Solvent was evaporated on rotovap. The crude solid was washed with hexane, redissolved in CH₂Cl₂ and filtered. Removal of solvent gave 90 mg (61.3%) of white solid. ¹H-NMR (acetone-d₆, 400 MHz, ppm): δ −0.13 (broad d, 6H), 2.21 (s, 12H), 2.30 (s, 6H), 6.57-6.60 (m, 2H), 7.02 (s, 4H), 7.23 (td, 2H), 7.34 (d, 2H), 7.44 (s, 2H), 7.52 (d, 2H).

It is understood that the various embodiments described herein are by way of example only, and are not intended to limit the scope of the invention. For example, many of the materials and structures described herein may be substituted with other materials and structures without deviating from the spirit of the invention. The present invention as claimed may therefore includes variations from the particular examples and preferred embodiments described herein, as will be apparent to one of skill in the art. It is understood that various theories as to why the invention works are not intended to be limiting. 

The invention claimed is:
 1. A first device comprising an organic light emitting device, further comprising: an anode; a cathode; and an organic layer, disposed between the anode and the cathode, the organic layer comprising an emissive dopant and a first host material comprising a carbene ligand coordinated to a three coordinate copper atom, wherein the first host material has the formula:

wherein Cu is a monovalent copper atom; wherein the carbene represented by X₁—C*—X₂ is a monodentate ligand selected from the group consisting of

wherein z is 1, 2, 3, or 4; wherein each of Y₁ and Y₂ form a bond with Cu; wherein at least one of (i) to (x) is true: (i) Y₁-Y₂ is selected from the group consisting of:

(ii) Y₁-Y₂ is selected from the group consisting of:

(iii) Y₁ is

and Y₂ is a monodentate ligand selected from the group consisting of

(iv) Y₁-Y₂ is selected from the group consisting of:

(v) Y₁-Y₂ is selected from the group consisting of:

(vi) Y₁-Y₂ is selected from the group consisting of:

(vii) Y₁-Y₂ is selected from the group consisting of:

(viii) Y₁-Y₂ is selected from the group consisting of:

(ix) Y₁-Y₂ is selected from the group consisting of:

and (x) Y₁-Y₂ is selected from the group consisting of:

wherein, when present, X is selected from the group consisting of NR, O, S, Se, CR₂, and CO; each R is independently selected from the group consisting of hydrogen, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl, and heteroaryl; Y₃ and Y₄ are independently selected from the group consisting of hydrogen, alkyl, aryl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, and heteroaryl; Y₃ and Y₄ are optionally joined to form a cycle, which may be extended by fusion n is 0, 1, or 2, and m is 0, 1, or
 2. 2. The device of claim 1, wherein Y₁-Y₂ is selected from the group consisting of:


3. The device of claim 1, wherein Y₁-Y₂ is selected from the group consisting of:


4. The device of claim 1, wherein Y₁ is

and Y₂ is a monodentate ligand selected from the group consisting of


5. The device of claim 1, wherein Y₁-Y₂ is selected from the group consisting of:


6. The device of claim 1, wherein Y₁-Y₂ is selected from the group consisting of:


7. The device of claim 1, wherein Y₁-Y₂ is selected from the group consisting of:


8. The device of claim 1, wherein Y₁-Y₂ is selected from the group consisting of:


9. The device of claim 1, wherein Y₁-Y₂ is selected from the group consisting of:


10. The device of claim 1, wherein Y₁-Y₂ is selected from the group consisting of:


11. The device of claim 1, wherein Y₁-Y₂ is selected from the group consisting of:


12. The device of claim 1, wherein the first host meets one of option (iv) and option (v), and Y₃ and Y₄ are selected from the group consisting of the following (a) to (e):

wherein, in each of (a) to (e), the dashed lines represent bonds to the boron (B).
 13. A first device comprising an organic light emitting device, further comprising: an anode; a cathode; and an organic layer, disposed between the anode and the cathode, the organic layer comprising an emissive dopant and a first host material selected from the group consisting of:


14. The device of claim 13, wherein the first host material is selected from the group consisting of:


15. The device of claim 13, wherein the first host material is selected from the group consisting of:


16. The device of claim 13, wherein the first host material is selected from the group consisting of:


17. The device of claim 13, wherein the first host material is selected from the group consisting of: 